Biomedical subjects

K Flood

Publications and source records attributed to K Flood.

10 recordsLinked to original sources

PubMed2005

Direct measurements of Ab and Ac using vertex and kaon charge tags at the SLAC detector.

Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst).

Journal Article↗

PubMed2003

Improved direct measurement of the parity-violation parameter Ab using a mass tag and momentum-weighted track charge.

We present an improved direct measurement of the parity-violation parameter A(b) in the Z boson-b-quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z-->bb events via the topological reconstruction of the B hadron mass. Manipulation of the Stanford Linear Collider electron-beam polarization permits the measurement of A(b) to be made independently of other Z-pole coupling parameters. From the 1996-1998 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A(b)=0.906+/-0.022(stat)+/-0.023(syst).

Journal Article↗

PubMed2002

Improved direct measurement of A(b) and A(c) at the Z(0) pole using a lepton tag.

The parity violation parameters A(b) and A(c) of the Zb(b) and Zc(c) couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the Z(0) pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-1998 SLD sample of 550,000 Z(0) decays produced with highly polarized electron beams, we measure A(b) = 0.919+/-0.030(stat)+/-0.024(syst), and A(c) = 0.583+/-0.055(stat)+/-0.055(syst).

Journal Article↗

PubMed2001

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons.

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.

Journal Article↗

PubMed2001

First symmetry tests in polarized Z0 decays to bbg.

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.

Journal Article↗

PubMed2000

High-precision measurement of the left-right Z Boson cross-section asymmetry.

We present a measurement of the left-right cross-section asymmetry ( A(LR)) for Z boson production by e(+)e(-) collisions. The measurement includes the final data taken with the SLD detector at the SLAC Linear Collider during the period 1996-1998. Using a sample of 383 487 Z decays collected during the 1996-1998 runs we measure the pole value of the asymmetry, A(0)(LR), to be 0.150 56+/-0.002 39 which is equivalent to an effective weak mixing angle of sin (2)straight theta(eff)(W) = 0.231 07+/-0.000 30. Our result for the complete 1992-1998 data set comprising approximately 537 000 Z decays is sin (2)straight theta(eff)(W) = 0.230 97+/-0.000 27.

Journal Article↗

PubMed1998

Formulation and characterization of new layered diffusional matrices for zero-order sustained release.

Statistical designs were used to study the effect of certain matrix formulation variables on the vitro release of a model compound, pseudoephedrine hydrochloride, from layered diffusional matrices designed for zero-order sustained release. These matrices consist of non-swellable, hydrophobic middle layers containing the active drug to which hydrophilic and/or hydrophobic barrier layers are press-coated. In general, linear release profiles can be obtained by applying hydrophilic barrier layers on both faces of a hydrophobic matrix tablet, or by applying a hydrophilic barrier layer on one face and a hydrophobic barrier layer on the other face of the matrix tablet. However, formulation and matrix variables in the barrier layers need to be controlled in order to achieve zero-order drug release from a hydrophobic matrix tablet coated with hydrophobic barrier layers on both faces.

Delayed-Action Preparations↗

PubMed1998

Design and evaluation of layered diffusional matrices for zero-order sustained-release.

New layered matrix systems designed for zero-order sustained release are presented. The devices consist of a hydrophobic middle layer and press-coated hydrophillic and/or hydrophobic barrier layer(s). The systems overcome the inherent disadvantage of non-linear release associated with diffusion-controlled matrix devices by providing additional releasing surface with time to compensate for the decreasing release rate. The in vitro release of pseudoephedrine hydrochloride as a model compound from the matrices was examined. Modulation of release from a selected matrix containing aminophylline was evaluated in a crossover study using nine beagle dogs. Preliminary in vitro/in vivo correlation was also studied. The systems described in this paper can potentially be scaled up to commercial production.

Aminophylline↗

PubMed1997

MK-801 neurotoxicity in the guinea pig cerebral cortex: susceptibility and regional differences compared with the rat.

N-methyl-D-aspartate (NMDA) receptor antagonists induce transient vacuole formation in neurons of the retrosplenial cortex and, after higher doses, necrosis in the same region. To our knowledge, all studies demonstrating these effects have been carried out in rats or mice. The present study investigated whether vacuolization occurs in the guinea pig, rats being used as controls. Female Dunkin-Hartley guinea pigs (age 15-18 weeks) were given a single subcutaneous injection of saline or the non-competitive NMDA antagonist dizocilpine maleate [(+)-MK-801; 1, 4, or 12 mg/kg]. Female Sprague-Dawley rats (age 16 weeks) received saline or MK-801 (1 mg/kg). Whatever the dose of MK-801, guinea pigs showed only occasional vacuolated neurons in the retrosplenial cortex. However, affected neurons (mainly large pyramidal cells of layer V) were found in the frontoparietal neocortex. The reaction was limited after 1 mg/kg, and seemed to reach a maximum at 4 mg/kg. Rats injected with 1 mg/kg MK-801 showed an intense vacuole reaction in neurons from layers III-IV of the retrosplenial cortex, but no affected neurons were noted in neocortical areas. We conclude that there are significant species differences in susceptibility to, and location of, vacuolization induced by NMDA receptor antagonists.

Animals↗

PubMedDate not supplied

Trial of labor: a study of 110 patients.

STUDY OBJECTIVE: The purpose of the study was to determine whether epidural analgesia is unsafe for trial of labor (TOL). DESIGN: Retrospective chart review. SETTING: Inpatient obstetric department at a university medical center. PATIENTS: One hundred ten ASA physical status I and II term parturients who attempted a TOL between December 1987 and June 1988. INTERVENTIONS: All the parturients previously had low transverse uterine incisions and received continuous electronic fetal and uterine pressure monitoring throughout labor. All the parturients were offered epidural analgesia during labor with bupivacaine 0.25%. MEASUREMENTS AND MAIN RESULTS: Sixty-seven percent of the parturients had successful vaginal delivery. Fifty-one of the 110 parturients had epidural analgesia for labor. There were two complete uterine ruptures; neither had epidural catheters. Both of the complete ruptures presented with monitored fetal distress rather than abdominal pain. Both mothers and their infants recovered uneventfully. CONCLUSIONS: Uterine rupture presents as monitored fetal distress rather than abdominal pain. Thus, epidural analgesia can be used in patients attempting a TOL.

Analgesia, Epidural↗